Flexible casing



FLEXIBLE CA iled Apri\l 28, 173.1.

7 L l 7 L 1:?

I 19111670637: Dav/p E. TEMPL /Wfi/V,

Patented 31, 11933 PATENT oFF cE UNITED "ASTATESJ FLEXIBLE CASING David R. Templeman, Worcester, Mass assignor to The American Steel and Wire Company of New Jersey, a corporation of New Jersey 1 Application April 28, 1930. sw rm. 448,146

. iclaims (on. c r-12) I Thisinvention relates to flexible casing adapted to enclose and guide brake cables, boat and aeroplane steering controls,- flexible shafts and. the

like, and it is among the objects thereof to provide a casing which shall be extremely flexible and in which the strands cooperate to support each other when curved or subjected to strain and which shall be of such character as to prevent lealgage of lubricants rmm the interior to the exterior thereof.

Flexible tubing as heretofore constructed embodies" a plurality of helical strands or coils, usually: two in number, which are overlapped in such manner as to provide limited bending'without any great distortion of the tubes interior.-

In accordance with the present invention, the flexible casing is constructed of at least three strands or coils which are arranged to eliminate interference of the respective coils with each other when the tubing is subjected to bending, and in which the inner and outer coils are provided with flat surfaces which constitute the' inner and/ outr wall surfaces of the conduit. Y The. construction of the casing and the operative relation of the several coil strands is more I clearly illustrated in connection with the accompanying drawing constituting a part hereof, in which like reference'characters designate like parts, and inwhich Figure 'l'is a longitudinal sectional view of a flexible casing or tubing embodying the principles of this invention, and

'- Figure 2.isa diagrammatic viewillustrating the fee \ stantially uniformly spaced as shown in the drawing, and the cross, sections of coils B and C are complementary to the shape of the coil A, whereby maximum surface contact is provided for the respective coils. .The spacing designated b between the convolutions of coil B is substantially the same as the spacing 0 between the convolutions of coil C, and the spacing a between the convolutions of the coil A is substantially that of the coils B andCI w In Fig. 2 of the drawing, adjacent ends 'ofcoils f B and C are shown' as nearly touching at the top of the casing, whereas the bottom portions of the coils are widely separated. Such is the relative position of the coils when the casing is flexed or curved, the upper portion being the outside of the I radiusand, the bottom the inside of the radius.

- The outside dimensions of the casing, designated by the line D, is the same whether the tube is co straight or curved, and the inside diameter it also remains constant. On account of the fixed diameter the casing will not buckle when dullload of compression is applied in curved position. The

distance from the center of the coil A to the to inner surface E of the coil B and to thelouter surface F of coil C varies with the degree of bending of the casing, the distances being shorter at the outside of the radius and longer at the inside ofthe radius, as illustrated at the top and to bottom of Fig. 2 of the drawing.

On account of the relative movement of the coils when subjected to bending, they'are sub jected to somewhat the same stress as a helical spring would be stressed when forced out ofline,

this force being effective in returning the coils to their normal straight position shown in Fig. 1. Onaccount of the cross'sectional shape of the strands the forces acting on the coils when the casing is curved are somewhat relieved on account, so of the end pressure which counter-acts opposing forcefroni side movements. P v

Also on account of the complementary shape and the relation of the several strands, any force applied endwise assists in strengthening the 85, (cable when it is bent to a radius, on account ofthe fact that the round wire strand fsreenforced both inside and outside so that any appliedspressureis divided equally between the three strands. By means of the construction shown, all strands are uniformly in engagement and are not controlled in their bending movements by the specing ofv the respective strands as was a common limitation in the two strand casing heretofore constructed, and since there is no crowding of the coils, the casing maybe bent to a greater curvature than was heretofore possible with other forms of flexible tubing.

On account of the intimate contact and rela=' time.

tively large surface engagement of the several 0 coils, the casing will not shorten undercompression and for the same reasons the casing constitu'tes a leak prooflhous'ing which prevents the escape of grease through the joints of the strands.

has a wide field of application where flexibility and strength are" necessary as in steering con- I trols, for example.

Although one embodiment of the invention has been herein illustrated and described, it will no Because of the numerous advantages the casing v Will ill

be obvious to those skilled in the art that various modifications y be made in the details of construction without departing from the principles herein set forth.

I claim:

l. A flexible casing comprising a round coil, the members of which are round in cross-section, and inner and outer coil the members of which are of single radius T-shaped cross-section in overlapping engagement with said round coil, said r shaped coils having their fiat'surfac'es disposed to constitute the inner and outer walls of w 2. A flexible casing comprising three concentric coils, the members of the central coil being circular in cross-section, and the members of the innor and outer coils being substantially T-shaped in cross-section with their stems entering between successive members of the inner coil, and the outer faces of the T-shaped coils being flat transversely so as to provide longitudinally fiat outer and inner faces.

s. a flexible tubular casingof the character described having a flat exterior and a flat interior, end comprising a central core in the to of a said neeeneo i spiral, the members of which are circular in cross-section,;and inner and outer spiral shells, the cross-sectional size of the members of the shells being substantially the same and of substantially T-shape with the flat headportions thereof at the inner and outer sides respectively of the casing, the stem portions of the T-shaped members lying between successive coils of the central core and of concave config uration at opposite sides with the concave portions fitting the circular shapeof the adjacent members of the central core.

4. A flexible, tubular casing of the character described comprising a central core in the form of a spiral, the members of which are circular in cross-section, and inner and outer spiral shells, the cross-sectional size of the members of the shells being substantially the same and of substantially T-shape, the stem portions of the T- shaped members lying between successive coils of the central coil and being concaved at opposite sides and fitting the circular shape of the membersof the central core.

DAVID R. TEIM'PLEMAN. 

